1. Field of the Invention
The invention pertains generally to an apparatus and method for device design, prediction of its mechanical behavior and passive control of contact pressure using the phenomena of bending of wires subjected to axial loading, including the phenomenon of elastic stability, and with a particular emphasis on mechanical, electrical, optical, and heat removing devices.
2. Description of the Prior Art
The performance of many mechanical, electrical, optical and thermal devices is sensitive to the level of, and the changes in, contact pressure. For example, a flexible (“Euler”, “Cobra”, buckled beam) electrical test probe provides an attractive solution to making electrical contact to a large number of close-center probe pads in advanced packages for very large scale integration (VLSI) devices. The pressure provided by such a probe should be high enough to ensure sufficient electrical contact, but low enough not to crack the chip or to cause damage to the probe itself. A similar situation takes place in some fiber-optic based devices, such as, optical sensors, optical connectors, as well as in some heat removing devices. The produced pressure caused by the bent and/or buckled heat conducting wires or carbon nanotubes (CNTs) should be high enough for a satisfactory heat transfer performance of the thermal interface, but low enough not to cause damage to the hot body, which might be mechanically vulnerable, nor to the wires or the CNTs themselves. This requirement often imposes significant restrictions on, and difficulties in, how the wire-grid-array (WGA) is designed, manufactured, and operated. In some applications, such as, CNT-based advanced heat-sinks, it is practically impossible to create a viable and functionally reliable product, if effective and insightful predictive modeling, preferably based on an analytical approach, is introduced and carried out prior to actual design and manufacturing efforts.
Prior art solutions suffer from several deficiencies. Notably, several mechanical and physical design problems arise in connection with such an application, including:                a) Insufficient anchoring strength of the root portion of the rods, including weak adhesion to the base; and        b) Extraordinary variability of the diameters and lengths of the grown wires and, because of that, a significant variability and even uncertainty in the produced contact pressure.        
Accordingly, it would be advantageous to develop a device, a design methodology and practical solutions to enable one to realistically prescribe, thoroughly predict and effectively control the contact pressure. It would be further advantageous to examine different design options and develop simple and easy-to-use formulae and calculation procedures that enable a WGA designer to choose the appropriate materials and the adequate geometric characteristics of the WGA wires, and predict with high accuracy their mechanical behavior, including contact pressure, displacements, stresses and even the probability of functional and/or mechanical failure.